Yervoy (ipilimumab) is the first drug ever shown to help late-stage melanoma patients live longer. However, it does not cure the disease.

"Late-stage melanoma is devastating, with very few treatment options for patients, none of which previously prolonged a patient's life," Richard Pazdur, MD, director of the FDA's cancer drugs office, says in a news release.

In a clinical trial with 676 late-stage melanoma patients for whom all other treatments had failed -- and for whom surgery was not an option -- patients taking Yervoy survived an average of 10 months after starting treatment. Patients taking an experimental vaccine lived an average of 6.5 months.

Yervoy also appears to extend survival when used as a first-line treatment for inoperable stage III or stage IV melanoma, Bristol-Myers announced earlier this week. Details of the study will be reported at the June meeting of the American Society of Clinical Oncology.

Yervoy is a biologic therapy. It's a kind of man-made antibody (a monoclonal antibody) that blocks a crucial switch on immune cells called CTLA-4. Cancers use this switch to turn off the body's anticancer immune responses.

Most drugs like this come with possibly severe side effects, and Yervoy is no exception. The drug can provoke powerful autoimmune reactions in which the immune system attacks normal cells in the body. In clinical trials, nearly 13% of patients taking Yervoy had severe or fatal autoimmune reactions.

Because of these unusually severe side effects, Bristol-Myers has agreed to establish what the FDA calls a risk evaluation and mitigation strategy (REMS) to help doctors avoid and manage adverse reactions to Yervoy.